Pat the chicken breasts dry and season both sides with salt, black pepper, paprika, and Italian seasoning.
Heat the olive oil and butter in a skillet over medium-high heat.
Cook the chicken breasts 5 to 6 minutes on each side until golden brown and cooked through. Remove from skillet and set aside.
Add minced garlic to the same skillet and cook for 30 seconds until fragrant.
Pour in the chicken broth and scrape the pan to loosen browned bits.
Add heavy cream, Dijon mustard, and red pepper flakes, then simmer for 3 to 4 minutes.
Stir in the grated Parmesan cheese until melted and combined.
If a thicker sauce is desired, add the cornstarch slurry and cook until sauce thickens.
Return the cooked chicken breasts to the skillet and simmer 3 to 5 minutes, coating them with the creamy sauce.
Garnish with parsley and serve over pasta, rice, mashed potatoes, or vegetables.